Physicochemical Properties and Intestinal Mucus Mucoadhesion of Flammulina velutipes Polysaccharide Nanoliposomes: Effects of Particle Size and Sterol Composition

The effective intestinal delivery of immunoactive Flammulina velutipes polysaccharide (FVP) is important for translating its biological activity. In this study, FVP was incorporated into nanoliposomes to evaluate how particle size and sterol composition affect their physicochemical properties, immunological response, mucus interaction, and intestinal distribution. FVP-loaded liposomes were prepared with cholesterol (CH) or plant sterol ester (SE) at two size levels (100 and 200 nm), yielding clear and comparable size stratification. Compared with CH-containing liposomes, SE-containing liposomes exhibited higher zeta potential, encapsulation efficiency, and phase transition temperature. All formulations showed good cytocompatibility and preserved the immunostimulatory activity of FVP. In vitro mucus adhesion assays revealed stronger sustained mucus retention for CH-containing liposomes, whereas SE-containing liposomes displayed relatively weaker sustained adhesion. By contrast, the in vivo 2 h post-administration intestinal distribution study suggested a trend toward greater intestinal tissue penetration for the SE formulations than for their CH counterparts, with the most pronounced effects in the jejunum. In both systems, the 100 nm liposomes generally exhibited greater intestinal adhesion and penetration than the corresponding 200 nm liposomes. Overall, SE served as a more naturally derived membrane sterol with potential biological functionality and tended to improve intestinal tissue penetration, whereas the 100 nm formulations showed a more favorable intestinal distribution profile.